You will need to round the 2 values in the expression to the ten thousand place and then subtract them for the estimated answer.
24,953-13,758 (Original Expression)
24,953 is closer to 25,000 than 24,000, and 13,758 is closer to 14,000 than 13,000.
25,000-14,000 (Estimated Expression)
11,000 (Subtract to simplify the expression)
The answer is 11,000.